1. Field of the Invention
The present invention relates to an ink jet recorder, such as an ink jet printer having a purging apparatus for sucking ink from a ink jet head and a purging method therefor.
2. Description of Related Art
Ink jet printers are known generally as ink jet recorders for recording on recording media, such as sheets of paper, by ejecting ink onto them. FIG. 9 of the accompanying drawings shows part of a conventional ink jet printer, which includes a recording head unit P3 having a recording head P2. The head P2 has four ejection nozzles P4, each of which has ejection holes (not shown) opening in its front surface P5. The ejection nozzles eject different colored inks including black, yellow, cyan and magenta, respectively. Four ink cartridges P1 containing the respective colored inks are mounted replaceably on the head unit P3, and each connected to the corresponding nozzle P4. After each cartridge P1 is replaced with a new one, ink is supplied from the new cartridge to the head P2, and can be ejected from the associated nozzle P4.
The printer is provided with a purging device having a cap P6 and a suction pump (not shown) in order to purge the nozzles P4. The purging may be started manually by the user operating a switch on the printer, or automatically if a predetermined condition is satisfied. The purging is performed to prevent the defective ejection of ink which may be caused if the ink in or on the recording head P2 dries, or if air bubbles are produced in the ink, or if droplets of ink stick to the nozzle surfaces P5. Specifically, the purging of each nozzle P4 involves covering its nozzle surface P5 with a suction cap P6, and then developing negative pressure in the cap P6 by means of a suction pump (not shown), in order to suck ink from the head P2 through the cap P6 and discharge the sucked ink outside.
Conventionally, when the purging operation is performed for all four ejection nozzles P4 successively, the nozzle for ejecting black ink is purged last. Namely, the purging operation has been done in order of lighter color inks. However, when the purging operation is performed in order of lighter color inks, there is a problem that some color inks tend to dry during the operation, because only one nozzle can be capped by the cap p6 at a time.